Single site catalyst systems, such as metallocene catalyst systems, have been used for gas phase polymerization of olefins to produce polymers having properties useful for a wide variety of applications. The catalyst productivity for metallocene catalysts systems, i.e. the amount of polymer produced per gram of the metallocene catalyst system, however, remains less than optimal. Further, metallocene catalyst systems in gas phase fluidized bed reactors have a tendency to cause polymer build-up, i.e. fouling, which is usually referred to as agglomeration, chunking, and/or sheeting of the polymer within the reactor. As such, the polymerization of olefins in gas phase fluidized bed reactors is frequently hindered because the reactor must be shutdown for cleaning and removal of the polymer build-up.
There is a need, therefore, for improved methods for the gas phase polymerization of olefins using metallocene catalyst systems having increased catalyst productivity. There is also a need for improved methods for the gas phase polymerization of olefins using metallocene catalyst systems having a reduced tendency for fouling.